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GH-34001: [C++] Add more rvalue overload for Status::operator& #34002

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PragmaTwice wants to merge 1 commit into from
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GH-34001: [C++] Add more rvalue overload for Status::operator& #34002

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26 changes: 22 additions & 4 deletions cpp/src/arrow/status.h
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Original file line number Diff line number Diff line change
Expand Up @@ -157,8 +157,10 @@ class ARROW_EXPORT [[nodiscard]] Status : public util::EqualityComparable<Status
inline bool Equals(const Status& s) const;

// AND the statuses.
inline Status operator&(const Status& s) const noexcept;
inline Status operator&(Status&& s) const noexcept;
inline Status operator&(const Status& s) const& noexcept;
inline Status operator&(const Status& s) && noexcept;
inline Status operator&(Status&& s) const& noexcept;
inline Status operator&(Status&& s) && noexcept;
Comment on lines +160 to +163

@cyb70289 cyb70289 Feb 8, 2023

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Looks to me "pass by value" is simpler. To reduce half of the functions. There might be overhead of an additional move, should be trivial.

Status operator&(Status s) const&;
Status operator&(Status s) &&;

@PragmaTwice PragmaTwice Apr 18, 2023 •
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I do not understand what you mean by the "simpler" that you mentioned.

It should be like this in c++23 or later:

template <typename Self, typename T>
    requires std::same_as<std::remove_cvref_t<T>, Status>
Status operator&(this Self&& self, T&& other) {
    if (ok()) return std::forward<T>(other);
    return std::forward<Self>(self);
}

(hand-written, you can check it by compiler and lang-server)

inline Status& operator&=(const Status& s) noexcept;
inline Status& operator&=(Status&& s) noexcept;

Expand Down Expand Up @@ -422,22 +424,38 @@ bool Status::Equals(const Status& s) const {
/// \cond FALSE
// (note: emits warnings on Doxygen < 1.8.15,
// see https://github.com/doxygen/doxygen/issues/6295)
Status Status::operator&(const Status& s) const noexcept {
Status Status::operator&(const Status& s) const& noexcept {
if (ok()) {
return s;
} else {
return *this;
}
}

Status Status::operator&(Status&& s) const noexcept {
Status Status::operator&(const Status& s) && noexcept {
if (ok()) {
return s;
} else {
return std::move(*this);
}
}

Status Status::operator&(Status&& s) const& noexcept {
if (ok()) {
return std::move(s);
} else {
return *this;
}
}

Status Status::operator&(Status&& s) && noexcept {
if (ok()) {
return std::move(s);
} else {
return std::move(*this);
}
}

Status& Status::operator&=(const Status& s) noexcept {
if (ok() && !s.ok()) {
CopyFrom(s);
Expand Down
15 changes: 15 additions & 0 deletions cpp/src/arrow/status_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -104,6 +104,21 @@ TEST(StatusTest, AndStatus) {
res = Status::Invalid("foo") & Status::IOError("bar");
ASSERT_TRUE(res.IsInvalid());

ASSERT_TRUE((a & Status::OK()).ok());
ASSERT_TRUE((c & Status::OK()).IsInvalid());
ASSERT_TRUE((a & Status::IOError("")).IsIOError());
ASSERT_TRUE((c & Status::IOError("")).IsInvalid());

ASSERT_TRUE((Status::OK() & a).ok());
ASSERT_TRUE((Status::OK() & c).IsInvalid());
ASSERT_TRUE((Status::IOError("") & a).IsIOError());
ASSERT_TRUE((Status::IOError("") & c).IsIOError());

ASSERT_TRUE((Status::OK() & Status::OK()).ok());
ASSERT_TRUE((Status::Invalid("") & Status::OK()).IsInvalid());
ASSERT_TRUE((Status::OK() & Status::IOError("")).IsIOError());
ASSERT_TRUE((Status::IOError("") & Status::Invalid("")).IsIOError());

res = Status::OK();
res &= Status::OK();
ASSERT_TRUE(res.ok());
Expand Down